Donald Trump and Hillary Clinton may not be the only candidates on the presidential debate stage this fall if enough voters are still looking for an alternative after the conventions.

Libertarian Party candidate Gary Johnson, a former governor of New Mexico, needs to score an average of 15 percent support in the most recent major polls after Labor Day to get his invitation. It’s not a far-fetched possibility.

“We’d be at a level where we’d be in the debates, and if that happens, anything is possible, meaning getting elected is possible,” he said.

Anti-Trump Republicans Mitt Romney and Jeb Bush have said they are considering voting for Johnson in November.

The Green Party candidate, Dr. Jill Stein, is trying to rally disaffected Bernie Sanders supporters to her banner so she can qualify, too. She faces a steeper climb. She had 6 percent support in the NBC poll and 5 percent in the ABC and CNN surveys.

The debates are scheduled for Sept. 26 in Dayton, Ohio; Oct. 9 in St. Louis and Oct. 19 in Las Vegas.